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FreeBSD-SA-13:10.sctp                                       Security Advisory
                                                          The FreeBSD Project

Topic:          Kernel memory disclosure in sctp(4)

Category:       core
Module:         sctp
Announced:      2013-08-22
Credits:        Julian Seward, Michael Tuexen
Affects:        All supported versions of FreeBSD.
Corrected:      2013-08-15 04:25:16 UTC (stable/9, 9.2-PRERELEASE)
                2013-08-15 05:14:20 UTC (releng/9.2, 9.2-RC1-p1)
                2013-08-15 05:14:20 UTC (releng/9.2, 9.2-RC2)
                2013-08-22 00:51:48 UTC (releng/9.1, 9.1-RELEASE-p6)
                2013-08-15 04:35:25 UTC (stable/8, 8.4-STABLE)
                2013-08-22 00:51:56 UTC (releng/8.4, 8.4-RELEASE-p3)
                2013-08-22 00:51:56 UTC (releng/8.3, 8.3-RELEASE-p10)
CVE Name:       CVE-2013-5209

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:http://security.FreeBSD.org/>.

0.   Revision History

v1.0  2013-08-22 Initial release.
v1.1  2013-09-07 Binary patch released for 9.2-RC1.

I.   Background

The SCTP protocol provides reliable, flow-controlled, two-way transmission
of data.  It is a message oriented protocol and can support the SOCK_STREAM
and SOCK_SEQPACKET abstractions.

The SCTP protocol checks the integrity of messages by validating the state
cookie information that is returned from the peer.

II.  Problem Description

When initializing the SCTP state cookie being sent in INIT-ACK chunks,
a buffer allocated from the kernel stack is not completely initialized.

III. Impact

Fragments of kernel memory may be included in SCTP packets and
transmitted over the network.  For each SCTP session, there are two
separate instances in which a 4-byte fragment may be transmitted.

This memory might contain sensitive information, such as portions of the
file cache or terminal buffers.  This information might be directly
useful, or it might be leveraged to obtain elevated privileges in
some way.  For example, a terminal buffer might include a user-entered
password.

IV.  Workaround

No workaround is available, but systems not using the SCTP protocol
are not vulnerable.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

2) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch http://security.FreeBSD.org/patches/SA-13:10/sctp.patch
# fetch http://security.FreeBSD.org/patches/SA-13:10/sctp.patch.asc
# gpg --verify sctp.patch.asc

b) Apply the patch.

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:http://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

3) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/8/                                                         r254354
releng/8.3/                                                       r254632
releng/8.4/                                                       r254632
stable/9/                                                         r254352
releng/9.1/                                                       r254631
releng/9.2/                                                       r254355
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:http://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<other info on vulnerability>

<URL:http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-5209>

The latest revision of this advisory is available at
<URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-13:10.sctp.asc>
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